JPS6350380A - Protection of concrete - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (a) Purpose of the invention "Field of industrial application" The present invention relates to a method for protecting concrete that is widely used in buildings and structures, and particularly relates to a method for protecting concrete that has recently been viewed as a problem. This article concerns concrete protection methods to prevent concrete deterioration due to alkaline aggregate reactions, as well as abnormal cracks in concrete that are thought to be caused by this. It is particularly effective in protecting progressing concrete and can be widely used in the civil engineering and construction industry.

``Conventional technology'' Concrete is used in large quantities in buildings and structures, and aggregate is essential for that concrete.
In recent years, due to the depletion of high-quality concrete aggregate resources, crushed stone and sea sand have come to be frequently used as concrete aggregates.

However, in the presence of alkali and water brought in by the use of alkali contained in cement and sea sand, some types of crushed stone undergo a chemical reaction, an expansion reaction called an alkali aggregate reaction, which causes abnormal cracks in the concrete. There is something that makes me

Three types of alkali aggregate reactions are known: alkali-silica reactions, alkali silicate reactions, and alkali carbonate reactions. Among these, the one that is currently causing problems in concrete is mainly called alkali-silica reactions. It is.

ASTM C33 lists proteinaceous stone, jadeite, phosphosilicate, cristobalite, certain volcanic rocks, zeolite, phyllite, etc. as minerals that may cause an alkali-silica reaction.

The alkali-silica reaction is known as a phenomenon in which aggregates containing the minerals mentioned above react with monovalent alkali metals such as IJ cum and potassium to produce alkali silicate, which absorbs and expands.

Although the reaction forms of the alkali silicate reaction and alkali carbonate reaction are different, both are expansion reactions due to the action of reactive aggregate, alkali, and water.

In order to prevent alkaline aggregate reactions, it has been proposed to reduce the alkaline content in concrete and to use non-reactive aggregates, but these alone are not sufficient preventive measures. The reasons for this are listed below.

This is not a measure for structures that

■ Judgment pressure for reactivity and non-reactivity The mortar bar method and other chemical methods used are not methods that can accurately grasp the behavior of aggregate in concrete.

■ The use of crushed stone and sea sand is unavoidable in the current aggregate situation, there are technical and economic limits to reducing monovalent alkali in cement, and in coastal areas there are For reasons such as the possibility of infiltration, it is almost impossible to reduce the amount of alkali in concrete to a point where it is not a problem.

Therefore, there is currently a strong need for a method of protecting concrete by preventing alkaline aggregate reactions in concrete, particularly a suitable method of protecting already poured concrete.

One of the methods being considered is to apply various coating materials to concrete to prevent water from entering the concrete and to suppress the progress of the alkaline aggregate reaction. At present, it has not been discovered yet.

In other words, when a thermosetting resin such as epoxy resin or polyester is used as a coating material, it is rigid and not flexible, so it cannot follow even the slightest movement of the structure, resulting in cracking and peeling. Synthetic rubbers such as urethane, butadiene, and chloroprene have elasticity but lack weather resistance, so they all deteriorate in a short period of time and have a problem in that their waterproof function decreases. Furthermore, since the above-mentioned coating materials have low water vapor permeability, there is a problem in that water that is present in the concrete before coating or water that has entered through waterproofing defects such as cracks and unpainted areas is contained, promoting alkaline aggregate reaction. It also has points.

In other words, when covering concrete surfaces with moisture-impermeable coatings such as those described above, it is virtually impossible to cover all the surfaces of civil engineering and architectural structures made of concrete with such coatings, and A certain amount of water intrusion is unavoidable due to infiltration from inside or condensation, and moisture often accumulates inside the concrete (in such cases, a moisture-impermeable coating will not harm the concrete). However, it does not play any effective role.

On the other hand, some so-called lacquer-type paints, which are made by dissolving synthetic resin in an organic solvent, have a certain level of water vapor permeability when applied thinly, but such thinly applied paints may not have sufficient waterproof performance. At the same time, it also has the problem of poor follow-up performance against cracks in concrete.

On the other hand, synthetic resin emulsion coatings such as acrylic resin emulsions, ethylene acetate vinyl emulsions, and vinyl acetate emulsions have moisture permeability, but because of their water absorption properties, if they come into contact with water for a long time, water may penetrate. It has the problem of allowing

[Problem that the invention seeks to solve]

The present inventors have solved the above problems, prevented water from entering concrete, quickly released the water stagnant inside, and prevented the concrete from expanding and breaking due to the alkaline aggregate reaction. The present invention was completed after various studies to find a coating material that maintains its functions well over time, and the present invention was made in search of an excellent method for protecting concrete.

(B) Structure of the Invention ``Means for Solving the Problems'' The present invention relates to a method for protecting concrete, particularly a method for efficiently preventing an alkali aggregate reaction occurring in concrete. The present invention relates to a method for protecting concrete, which comprises coating the surface of concrete with an aqueous dispersion of an acrylic resin having a glass transition temperature of 10° C. or lower.

O-alkoxysilane compound The alkoxysilane compound in the present invention is generally a compound represented by the following formula.

R4-o-8i(OR1)n Preferred alkoxysilane compounds for the present invention are those in which R' is an alkyl group or oxyalkyl group having 1 to 4 carbon atoms, and R is any alkyl group or alkylene group a. , aryl group, cycloalkyl group, n is 2~
It is an integer of 3.

More preferred alkoxysilane compounds for the present invention include an alkyl group in which R' has 1 to 4 carbon atoms;
In particular, those having a methyl group or an ethyl group, and R is 1 to 1
an alkyl or alkylene group having 7 carbon atoms,
Particular preference is given to alkyl groups having 3 to 12 carbon atoms, and those having 5 atoms.

It is preferable to avoid those with a large number of carbon atoms in R', as they will decrease the reactivity. It is preferable to avoid this as it may lead to a decrease in

Specific examples of alkoxysilane compounds include the following.

Methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, Pentyltrimethoxysilane, pentyltriethoxysilane, decyltrimethoxysilane,
Decyltriethoxysilane, stearyltrimethoxysilane, stearyltriethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane, dimethyldimethoxysilane.

Among these alkoxysilane compounds, particularly preferred for the present invention are n-propyltrimethoxysilane,
1so-propyltrimethoxysilane, n-butyltrimethoxysilane, 1so-butyltrimethoxysilane,
These are tcrt-butyltrimethoxysilane, n-hexyltrimethoxysilane, and n-decyltrimethoxysilane.

In the present invention, these alkoxysilane compounds are preferably used as a solution by dissolving them in an organic bath agent, or as a dispersion in water.

Examples of organic solvents include hydrocarbon solvents such as mineral spirit, naphtha, and kerosene, alcohol solvents such as methanol, ethanol, and isopropyl alcohol, mixed solvents of these and water, and aromatic solvents such as toluene and xylene. .

The concentration of the alkoxysilane compound in the solution or dispersion is determined depending on the amount applied to the concrete and is not uniform, but it is preferably about 1 or more, more preferably 5 to 40. If the concentration is less than 1%, it is difficult to provide a waterproof function. Although there is no problem in terms of performance when the concentration is high, a preferable range of about 40% or less is mainly from an economic point of view.

O Acrylic resin The acrylic resin in the present invention preferably contains at least 20% of acrylic esters and methacrylic esters.
It is a polymer obtained by polymerizing a monomer or monomer mixture containing ~1oos, more preferably 40 to 100%, particularly preferably 70 to 100%, by a normal polymerization method, and is generally combined with an acrylic resin. It comprehensively includes what is being said.

Specific examples of the above acrylic esters and methacrylic esters include methyl acrylic acid and methacrylic acid,
Ethyl, n-propyl, is.

-Propyl, n-butyl, 1so-butyl, 5ee-
Butyl, n-amyl, 1so-amyl, n-hexyl,
Examples include esters such as n-hebutyl, oxoheptyl, n-octyl, 2-ethylhexyl, n-nonyl, oxononyl, n-decyl, and oxodecyl.

In addition to the above-mentioned acrylic acid alkyl esters, there are vinyl monomers that can be copolymerized with acrylic esters and methacrylic esters as monomers constituting acrylic resins, and specifically, acrylic acid or Methacrylic acid, ethylene, vinyl acetate, vinyl chloride, vinylidene chloride acrylonitrile, styrene, butadiene, acrylamide, methylol acrylamide, vinyl propionate, itaconic acid and its esters, maleic acid and its esters, crotonic acid and its esters, @ o@e*f@a@@@@@gNh@Oe9e9&
Q) Examples include melolyloyloxyethyltrimethylammonium chloride.

If the amount of acrylic ester and methacrylic ester as constituent monomers of the acrylic resin used in the present invention is less than 20, the weather resistance of the resin itself may be reduced.

Furthermore, by copolymerizing acrylic acid, methacrylic acid, or other monomers, the toughness of the coating film can be improved and the coating film can be made less likely to crack.

On the other hand, if too much acrylic acid, methacrylic acid, or other monomers are compounded, the flexibility of the coating will decrease, the ability to follow cracks in the structure will decrease, and the waterproof function will tend to decrease. Of course, the above-mentioned M weatherability also poses a problem.

The acrylic resin used in the present invention has a glass transition temperature (hereinafter referred to as Tg point) of 10°C or less, and
The g point is the temperature at which the various properties of an amorphous polymer suddenly change, below which the motion of the molecular segments of the amorphous portion of the polymer is frozen.

To actually measure the Tg point of the resin used in the present invention, for example, the thermal expansion at various temperatures is measured, the specific volume is plotted against each temperature, and the resulting curve is bent. A common method for determining the temperature at a point is used.

However, in practice, when the Tg point value of a resin composed of individual monomers is known, the Tg of a copolymer resin is
The value of the point can be calculated using the following formula.

W: 1 amount fraction of component 1.

W2: Component 2.

Wn: weight fraction of component n.

Tg: Glass transition temperature of component 1 sole polymer (0K)
Tg,: #2 ('
K) Tgn: #n
('K) where w, +w, +... 10Wn=1
It is.

The Tg points of the main known single resins are listed below. All numbers within the arc are Tg points), polymethyl acrylate (8℃), polybutyl acrylate (-54℃), poly 2-ethylhexyl acrylate (-55℃). ), polymethyl methacrylate (105°C), polystyrene (100°C), polyvinyl acetate (60°C), polymethacrylic acid (160°C), etc.

Next, an example of calculating the Tg point of a copolymer resin is shown. The Tg point of a copolymer resin containing 701 parts of butyl acrylate (hereinafter abbreviated as "parts") and 60 parts of styrene is -23 DEG C. when calculated from the above formula.

The method for determining the Tg point has been explained above, but the Tg point of the acrylic resin in the present invention can be determined from the above formula and the Tg point (if not mentioned, refer to the Chemical Handbook published by Maruzen). It is.

The reason why a flexible resin with a Tg point of 10° C. or less is used in the present invention is to give the coating film the ability to follow vibrations of concrete structures, expansion and contraction caused by temperature differences, and cracks in the base.

If a hard resin with a Tg point exceeding 10° C. is used, the coating film will crack due to vibration, expansion/contraction, cracks, etc. of the structure, resulting in loss of waterproof properties.

Acrylic resins with a Tg point of 10°C or less are obtained by polymerizing acrylic esters and methacrylic esters as described above, and the acrylic resins used in the present invention include those having 6 to 10 carbon atoms and more. Preferably, those obtained by polymerizing an acrylic acid alkyl ester having 4 to 9 alkyl groups are preferred.

If a material having less than 6 carbon atoms is used, problems may arise in the water resistance and flexibility of the coating film, and if a material having more than 10 carbon atoms is used, there may be a problem in the strength of the coating film.

In the present invention, an aqueous dispersion in which an acrylic resin is dispersed in an aqueous medium is used.As for the aqueous dispersion, the monomers are polymerized by conventional emulsion polymerization using a commonly known emulsifier. It is preferable that the emulsion obtained by the above method has a solid content concentration of 30 to 70 particles. Of course, soapless emulsions, hydrosol emulsions, etc. can also be applied.

It is also possible to use in the present invention an aqueous dispersion of acrylic resin in which aggregates, short fibers, thickeners, surfactants, viscosity stabilizers, antifoaming agents, etc. are blended.

Examples of materials that can be used include talc, mica, acidic Shiratama, diatomaceous earth, kaolin, quartz, silica sand, cold water sand, iron powder, fly assy, satin white, titanium oxide, ferrite, lithopone, baryta, wood powder, and zirconia. , perlite, vermiculite, shirasu balloon, carbon black, bentonite, calcium carbonate, white carbon, and various cements such as portland cement, blast furnace cement, and alumina cement.

In addition, as short fibers, inorganic fibers, natural fibers, or synthetic fibers can be used, and specific examples include asbestos, rock wool, glass wool, slag wool, pulp, polyethylene fibers, polyvinyl chloride fibers, vinylon fibers, nylon fiber,
Acrylic fibers, polyester fibers, cotton, linen, etc. are used. As the thickener, modified cellulose such as methylcellulose and hydroxyethylcellulose, polyglycerides, polyethylene oxide, polyvinyl alcohol, water-soluble polyacrylates, polyacrylamide, alkali-thickened polyacrylate, etc. are used.

Surfactants are used to improve the dispersibility of aggregates, and examples of such surfactants include polyoxyethylene alkyls, alkylphenols, etc. Examples include esters such as sorbitan fatty acid, and oxyethylene-oxyglopylene block polymers.

As the viscosity stabilizer, for example, soda, potash, ammonium salts such as ligninsulfonic acid, polyacrylic acid, polymethacrylic acid, and tripolyphosphoric acid are used.

Further, antifoaming agents include octyl alcohol, caffryl alcohol, lauryl alcohol, and cyclohexanol.

O Construction method: Labor 1; Pi 2. y compound, object h 7'c 6 :
I: y j It is applied to the surface of the word by a conventional coating method such as a brush, roller, or airless spray.

The coating amount of Ax'R N'Ran compound is 0.05 to 2.0k.
The range of t/lri can be coated once or in several times. The preferred coating amount range is 0.2 to 1.0 kt/
It is rrl. If the application amount is less than 0.05 kl/m, effective waterproofing will not be achieved (2.0 kl/ni
If the amount exceeds 1, it will take a long time to apply, and the effect will not improve as much as the amount applied.

In the present invention, following the application of the alkoxysilane compound, an aqueous dispersion of an acrylic resin is applied, preferably at an interval of 5 hours or more. The coating interval is preferably one day or more. If the painting interval is less than 5 hours,
The alkoxysilane and/or solvent may have an adverse effect on the film formation of the acrylic resin and reduce weather resistance.

The aqueous dispersion of acrylic resin can be applied by brush,
Conventional methods such as roller or spray coating can be used.

The amount of coating is determined from α2 ky / rrj to 3.
The range is preferably 0 k)/ff7L'', more preferably 0.5 to 2.0 kg/771''. If the coating amount is less than 0.2 ky/rr1, there is a high possibility that waterproofing defects will occur due to a decrease in followability to cracks and uneven coating. If the coating amount exceeds 3.0 kg/rrj, it is not preferable because the drying film formation rate decreases and the crack following effect cannot be improved to the extent that the coating amount increases.

Other materials to be used In addition to the method of the present invention, it is possible and often preferable to use various types of books and materials in combination as long as the effects of the present invention are not significantly reduced.

For example, it is possible to provide an adhesion mediating layer between the alkoxysilane compound and the acrylic resin. The adhesion mediating layer contributes to improving the adhesion of the acrylic resin, and
Examples of what can be used include chlorinated olefin resins such as chlorinated polyethylene, chlorinated polypropylene, and vinylidene chloride.

It is also possible to apply a protective coating to the surface of the acrylic resin, which is effective in improving the weather resistance of the acrylic resin and preventing contamination.

Examples of protective materials include solvent-based acrylic paints and acrylic urethane paints, water-based emulsion paints, and polymer cement mortar.

"Function" Since the alkoxysilane compound used in the method of the present invention is a low-molecular compound, it penetrates deep into the concrete structure, and then silanol (]5i-OH
), changing the hydrophilic properties of concrete to hydrophobic properties. Also, since the capillaries in the concrete structure are not buried, water vapor permeability is not inhibited.

Acrylic resins with a glass transition temperature of 10°C or less form a water vapor permeable coating on the concrete surface to prevent water intrusion, especially when water pressure is applied, which is a disadvantage of alkoxysilane compounds. .

In addition, the acrylic resin has excellent weather resistance and its flexibility to follow the movement of concrete allows it to maintain good effects over a long period of time. As described above, the alkoxysilane compound and the acrylic resin complement each other's defects without interfering with each other's characteristics, and have the effect of forming a protective core covering layer suitable for preventing alkali aggregate reaction.

"Examples and Comparative Examples" The effects of the present invention will be specifically explained using Examples and Comparative Examples.

The test method and drugs used are as follows.

1) Preparation of alkaline aggregate reactive concrete specimens Concrete having the composition shown in Table 1 was poured into a 10×10×4 Daa iron mold, and after demolding the next day, it was cured in water at 20° C. for 14 days.

After leaving this specimen at 20°C and 60% RH for 1 day, alkoxysilane was applied, and after leaving it for another 1 day, an aqueous dispersion of acrylic resin was applied, and the specimen was left at 20°C and 60% RH for 7 days. It was left to dry for several days.

All coatings were carried out using...

2) Forced treatment conditions After the test specimens were left to stand under the conditions shown below, the effects of the present invention were evaluated based on the characteristic items shown in section 3).

■Outdoor @ Dew Test 2Left in the natural environment for 6 months in Minato Ward, Nagoya City.

(2) Salt water sprinkling test: A 100 cycle test was carried out in an atmosphere at 40° C., with one cycle consisting of 6% saline water sprinkling for 5 hours, stopping watering for 8 hours, and ventilation drying for 3 hours.

5) Characteristic items The effects of the present invention were determined based on the characteristics shown below.

■ Changes in appearance Changes in the appearance of the specimens after forced treatment were judged from visual pressure.

■ Dimensional changes in the specimen before and after the expansion ratio two forced treatments were measured using a contact gauge.

■ Weight change rate 2 The weight change rate of the specimen before and after the forced treatment was determined using the following formula.

■ Adhesion maintenance rate: From the adhesion of the coating material before and after the forced treatment test, the adhesion maintenance rate was calculated using the following formula.

Example 1 Adjustment of alkoxysilane did.

Production of aqueous dispersion of acrylic resin A composition consisting of 90 parts of 2-nitylhexyl acrylate, 8 parts of methyl methacrylate, 2 parts of acrylic acid, 2 parts of sodium dodecylbenzenesulfonate, 70.3 parts of ammonium persulfate, and 100 parts of water. Polymerization was carried out using a conventional method at a temperature of 70° C. for 5 hours to produce an acrylic side-containing emulsion with a solid content of 48 cm, and then ammonia was added to adjust the pH to 7.0.

The Tg point of the obtained acrylic resin was -46°C.

50 parts of calcium carbonate was mixed with the above emulsion per 100 parts of resin to obtain an aqueous acrylic resin dispersion.

Test specimens were prepared using the above alkoxysilane and acrylic resin aqueous dispersion, and various properties were measured.The test results are summarized in Table 4, and all exhibited good performance.

In other words, the test specimen showed the natural tendency of concrete to shrink, and its weight also decreased, indicating that it was transitioning to a dry state while releasing internal moisture.

Examples 2 to 7 The alkoxysilanes shown in Table 2 and the acrylic resin aqueous dispersions shown in Table 3 were produced in the same manner as in Example 1 except for the matters described in the tables, and test specimens were prepared.

The results of various characteristic evaluation tests for this are shown in Table 4. In all cases, there was no abnormality in appearance, and the weight change and length change of the test specimens each tended to decrease.

Comparative Examples 1 to 7 As shown in the comparative examples in Table 5, test specimens were prepared in the same manner as in Example 1 using the alkoxysilane obtained in Example, the acrylic resin aqueous dispersion obtained in Example, or a commercially available product. adjusted.

The results of various characteristic evaluation tests for this are shown in Comparative Examples in Table 5, and all results were significantly inferior to those obtained by the method of the present invention. That is, in the salt water sprinkling test, all test specimens had abnormalities in appearance, and most of the test specimens showed an increase in NI and a tendency to expand.

(C) Effects By applying the method of the present invention to concrete that is likely to undergo an alkali aggregate reaction or to concrete in which an alkali aggregate reaction is already in progress, it becomes possible to significantly delay the progress of the alkali aggregate reaction. Therefore, it is possible to reduce enormous economic losses due to alkaline aggregate reaction deterioration of civil engineering and architectural concrete, and at the same time, it is possible to significantly reduce the risk of human harm caused by concrete destruction.

In addition, the method of the present invention not only prevents alkaline aggregate reaction, but also prevents salt damage, which causes concrete deterioration.
It is a suitable protection method against frost damage, weathering, carbonation, etc., and is a great way to improve the durability of concrete structures.
It is something that contributes.

Claims (1)

[Claims] 1. A method for protecting concrete, which comprises applying an alkoxysilane compound to the surface of concrete and then further applying an aqueous dispersion of an acrylic resin having a glass transition temperature of 10° C. or less.